A study of
hadron matter, first of all, an interacting system of protons and neutrons,
has a long history; see, e.g.,
Refs. [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}.
Realistic versions of the nuclear matter equation of state includes both
the attractive and repulsive forces
between
particles.
Thermodynamical behavior of this matter
leads to the liquid-gas first-order phase transition
which ends at the critical point.
Experimentally, a presence of the liquid-gas phase transition
in nuclear matter was reported and then analyzed
in numerous papers
(see, e.g., Refs. [12]}, [13]}, [14]}, [15]}, [16]}, [17]}).
Critical points in different systems of hadrons were studied in
Refs. [18]}, [19]}, [20]}, [21]}, see also references therein.
